Experimental evaluation of continuous and pixelated dispersive optical phased arrays for 2D beam steering

Abstract

Dispersive optical phased arrays (DOPAs) offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation, and therefore low control complexity and low power consumption. However, in terms of scalability, state-of-the-art DOPAs do not easily achieve a balanced performance over the specifications of long range LiDAR, including the number of pixels (resolvable points) and beam quality. Here, we experimentally demonstrate the pixelated DOPA concept, which overcomes the scaling challenges of classical (continuous) DOPAs by introducing a new design degree of freedom: the discretization of the optical delay lines distribution network into blocks. We also present the first demonstration of the unbalanced splitter tree architecture for the DOPA distribution network, incorporated in both the continuous DOPA and the pixelated DOPA variations. The small-scale demonstration circuits can scan over a field of view of 15° × 7.2°, where the continuous DOPA provides 16 × 25 pixels, while the pixelated DOPA provides 4 × 25 pixels, for a 1500 to 1600 nm wavelength sweep. The pixelated DOPA exhibits a side lobe suppression ratio with a median of 7.6 dB, which is higher than that of the continuous version, with a median of 3.6 dB. In addition, the ratio of the main beam to the background radiation pattern is 11 dB (median value) for the pixelated DOPA, while for the continuous DOPA, it is 9.5 dB. This is an indication of a higher beam quality and lower phase errors in the pixelated DOPA. The degree of discretization, combined with other design parameters, will potentially enable better con trol over the beam quality, while setting practical values for the number of pixels for large-scale DOPAs.